I. Field of the Invention
The invention relates to cracking of hydrocarbons, generally classified in U.S. Patent Office, Class 208, subclasses 72, 73, 74, 113, 155, 157 and 164; and Class 422, subclasses 143-147.
II. Description of the Prior Art
Owen U.S. Pat. No. 3,886,060, FIG. 1, has a plurality of wyes or injectors 38' for introducing residual oil feeds 38 to the regenerated catalyst in the riser. FIG. 2 also shows a riser 27 which includes a plurality of wyes/injectors 37 for injecting oil into the riser to admix with regenerated catalyst 69.
Friedman U.S. Pat. No. 2,908,630 shows cracking apparatus including a reactor riser having a plurality of wyes or feeds for introducing oil to a freshly regenerated catalyst flowing within the riser. Three oil inlets 14a, 14b, and 14c are each fed oils having progressively greater coking factors.
Luckenbach U.S. Pat. No. 2,963,421 shows catalytic cracking apparatus having one or more feed nozzles 24 for feeding virgin unmixed gas oil to the riser.
Hettick U.S. Pat. No. 2,938,856 shows a riser 3 with a plurality of feeds 7-11 for introducing unmixed oil to a regenerated catalyst flowing within the riser.
Gomory U.S. Pat. No. 3,186,805 shows catalytic cracking apparatus in which regenerated catalyst and oil mixture is fed to the lower end of a riser at a plurality of locations.
James U.S. Pat. No. 3,964,876, FIG. 1, shows a three-stage riser 2 having a plurality of locations for feeding regenerated catalyst and including three zones 8, 9 and 10. The lower most zone has the smallest diameter and the upper most zone has the largest diameter.
Various other U.S. patents including Carr U.S. Pat. No. 3,639,228; Chou U.S. Pat. No. 4,578,183; and Buyan U.S. Pat. No. 4,650,566 disclose catalytic cracking apparatus having risers provided with at least three nozzles at their lower most region for introducing oil feeds to catalyst within the riser.
Various U.S. patents including Haunschild U.S. Pat. No. 4,417,974 and Mauleon U.S. Pat. No. 4,818,372 and U.S. Pat. No. 4,832,825 show cracking risers having two or more nozzles for feeding oils to the lower end of the riser.
None of the above patents teach, in combination, a multiple wye arrangement in which each wye has a short individual riser which is connected with a common (short) cracking riser so that neat feeds or unmixed feeds, e.g. diesel oil, contact clean regenerated catalyst before the catalyst enters the common riser. Since most cracking occurs before the individual oil-catalyst mixtures enter the common riser, the effect in the individual risers is similar to a riser cracker operating on a single unmixed feed. Thus the competitive cracking conventionally experienced when mixed feeds are cracked, is largely avoided.